There are descriptions about pyridone derivatives in, for example, Patent Document 1 and Non-Patent Document 1, but there are no descriptions on a herbicidal activity of the compounds described in those documents. Also, there has been reported in, for example, Patent Document 2 that a substituted cyclic dione compound has a herbicidal activity. However, a pyridone derivative of the present invention is not disclosed in those documents. Consequently, it can be said from the above that a pyridone derivative represented by Formula [1] has a herbicidal activity is not known upon the face of documents.
Patent Document 1: WO 2004/043924
Patent Document 2: EP No. 283261
Non-Patent Document 1: Helvetica Chimica Acta, 1988, Vol. 71, p. 596